Download MendeleyCocrystallization of the Src-Family Kinase Hck with the ATP-Site Inhibitor A-419259 Stabilizes an Extended Activation Loop Conformation.
Selzer, A.M., Alvarado, J.J., Smithgall, T.E.(2024) Biochemistry 63: 2594-2601
- PubMed: 39315638 Search on PubMed
- DOI: https://doi.org/10.1021/acs.biochem.4c00323
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9BYJ - PubMed Abstract:
Hematopoietic cell kinase (Hck) is a member of the Src kinase family and is a promising drug target in myeloid leukemias. Here, we report the crystal structure of human Hck in complex with the pyrrolopyrimidine inhibitor A-419259, determined at a resolution of 1.8 Å. This structure reveals the complete Hck active site in the presence of A-419259, including the αC-helix, the DFG motif, and the activation loop. A-419259 binds at the ATP-site of Hck and induces an overall closed conformation of the kinase with the regulatory SH3 and SH2 domains bound intramolecularly to their respective internal ligands. A-419259 stabilizes the DFG-in/αC-helix-out conformation observed previously with Hck and the pyrazolopyrimidine inhibitor PP1 (PDB: 1QCF). However, the activation loop conformations are distinct, with PP1 inducing a folded loop structure with the tyrosine autophosphorylation site (Tyr416) pointing into the ATP binding site, while A-419259 stabilizes an extended loop conformation with Tyr416 facing out into the solvent. Autophosphorylation also induces activation loop extension and significantly reduces the Hck sensitivity to PP1 but not A-419259. In cancer cells where Hck is constitutively active, the extended autophosphorylation loop may render Hck more sensitive to inhibitors like A-419259 which prefer this kinase conformation. More generally, these results provide additional insight into targeted kinase inhibitor design and how conformational preferences of inhibitors may impact selectivity and potency.
- Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, 450 Technology Drive, Pittsburgh, Pennsylvania PA 15219, United States.
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